Effect of Coupon Area on Evaluation Results of DC Interference Degree of Buried Pipeline Under Damaged Coating

Aiming at the influence of stray current interference on buried oil and gas pipelines, the influence of coupon area on the evaluation of DC interference degree of buried pipelines under damaged coatings was studied based on field investigation. The relationship among DC interference voltage and coupon area, current density and corrosion rate was discussed. The results showed that the current density of the test piece was positively correlated with the interference voltage and negatively correlated with coupon area. Under the same interference voltage, the current density and corrosion rate of the coupon increased with the decrease of coupon area, and the corrosion rate of the 1 cm² coupon was 4.70 times that of the 6.5 cm² coupon. When the area of the coupon was the same, the corrosion rate increased with the increase of interference voltage. When evaluating the risk of local corrosion of pipelines, for pipeline sections with obvious DC interference, it was recommended to use 1-6.5 cm² coupons for corrosion degree evaluation, 1 cm² test pieces for pitting evaluation, and 6.5 cm² coupon for uniform corrosion evaluation.